In order to forge workpieces with a distinct longitudinal axis, use is made of forging machines provided with three or more rams which are angularly distributed in one plane transverse to said axis, and in particular four rams which are arranged offset at 90.degree. to one another in a cruciform manner, act radially upon the workpiece which is guided longitudinally on the system axis, and are equipped with forging tools. It is structurally advantageous if the rams, guided in a machine frame, are constructed, at their ends remote from the tools, (or dies) in the form of fluid-pressure cylinders open towards the outside and containing static pistons, or are connected to such piston-cylinder units.
Because of the considerable forming capacity of these radial-forming forging machines, a high degree of confinement, preferably complete encirclement, of the workpiece has to be provided in the forming region. To this end, the tools should form a closed pass contour in adjustable inner end positions of the stroke, for which purpose the tools can be set and fixed in their common plane, transversely to the rams by means of tool supports and displacement devices acting upon the tool supports, as a function of the setting of the inner end position of the stroke of the rams, in such a way that the part of the operating face of each tool exceeding the pass-contour dimension is covered by a lateral face of the adjacent tool.
If the forging machine is to be used for open-die fine forging, it is recommended that the piston-cylinder units should be dimensioned in accordance with the operating stroke of the ram in order to minimize the compression volume, this being an essential pre-condition for rapid-stroke operation. The stroke position, by which the pass contour bounded by the tools is defined, can be set by adjustment of crossheads displaceable with respect to the machine frame and supporting the pistons of the piston-cylinder units. If, on the other hand, the forging machine is used for open-die stretch or elongation forging, the piston-cylinder units can be dimensioned for the entire ram stroke, so that fixed crossheads can be provided for supporting the pistons, and the end positions of the stroke of the rams can be set by displaceable or replaceable stops.
The invention relates to forging machines of the above-described type, and in particular to the design of the displacement devices acting upon the tool supports for setting the tools with respect to the rams in accordance with the end position of the stroke of the rams. It is known to use displacement devices which are provided with drive devices situated on the outside adjacent to the rams, as known from U.S. Pat. Nos. 4,831,864, 4,813,263 and 4,796,456, , corresponding to European Patent EP 0 228 030 B1, FIGS. 2, 8 and 9, and from U.S. Pat. Nos. 5,313,816 and is 5,293,769 corresponding to EP 0 549 825 B1. The known displacement devices have the disadvantage that the connection of the displacement devices to their drives must be provided with couplings or transmission connections which compensate or allow for the stroke of the rams and which have to be dimensioned for the total stroke of the rams when the drives are attached rigidly to the frame (EP 0 549 825B1) or at least for the operating stroke of the rams when the drives are attached rigidly to the crosshead for setting the stroke position (EP 0 228 030 B1, FIGS. 7, 8 and 9).